Molecular evolution of GII.P17-GII.17 norovirus associated with sporadic acute gastroenteritis cases during 2013-2018 in Zhoushan Islands, China.

In this study, we investigated the molecular characteristics and spatio-temporal dynamics of GII.P17-GII.17 norovirus in Zhoushan Islands during 2013-2018. We collected 1849 samples from sporadic acute gastroenteritis patients between January 2013 and August 2018 in Zhoushan Islands, China. Among the 1849 samples, 134 (7.24%) samples were positive for human norovirus (HuNoV). The complete sequence of GII.17 VP1 gene was amplified from 31 HuNoV-positive samples and sequenced. A phylogenetic tree was constructed based on the full-length sequence of the VP1 gene. Phylogenetic analysis revealed that the GII.17 genotype detected during 2014-2018 belongs to the new GII.17 Kawasaki variant. Divergence analysis revealed that the time of the most recent common ancestor (TMRCA) of GII.17 in Zhoushan Islands was estimated to be between 1997 and 1998. The evolutionary rate of the VP1 gene of the GII.17 genotype norovirus was 1.14 × 10-3 (95% HPD: 0.62-1.73 × 10-3) nucleotide substitutions/site/year. The spatio-temporal diffusion analysis of the GII.17 genotype identified Hong Kong as the epicenter for GII.17 dissemination. The VP1 gene sequence of Zhoushan Island isolates correlated with that of Hong Kong and Japan isolates.